1. Field
The present invention relates to a hydrorepellent composition, for example a super-hydrorepellent coating composition, a super-hydrorepellent coating layer including a cured product of the super-hydrorepellent coating composition, and a heat exchanger including the super-hydrorepellent coating layer.
2. Description of the Related Art
FIG. 1 is a schematic view of a heat exchanger conventionally used in a refrigerator. When high-temperature/wet air flows between a refrigerant pipe and a cooling fin which are maintained at a temperature below a freezing point and heat exchange occurs, frost is formed on the surface of the refrigerant pipe and the cooling fin. Frost continues to grow until the refrigerant pipe and the cooling fin are completely covered by frost or the air flow stops. Once the frost is formed, it intercept the air flow and prevent air cycling. In addition, the formed frost act as a heat resistor and hinder the heat exchange, thereby decreasing a cooling efficiency. Accordingly, a method of defrosting the refrigerant pipe and the cooling fin is required.
According to currently available defrosting methods, frost is removed by heat generated by a heater. Examples of defrosting methods using a heater include a method of defrosting by circulation of air that has been heated by a heater located at a lower portion of a heat exchanger, and a method of defrosting by thermal conduction caused by a heater in a heat exchanger. When these methods are used, however, electric power consumption for defrosting occurs.
Accordingly, studies for reducing electric power consumption required for defrosting by performing a hydrophilic or hydrorepellent treatment on the surface of the heat exchanger to obtain uniform frost formation and a short defrosting time are being performed. The following techniques provide hydro-repellent properties to the heat exchanger.
First, as illustrated in FIG. 2A, a hydrorepellent fluorine-substituted polymer layer may be used. For example, a polymer layer formed by polymerizing a material containing a fluorocarbon group and a chlorosilane group, or a polymer layer formed by polymerizing a material containing a fluorocarbon group and an alkoxysilane group are formed on the surface of a heat exchanger.
Second, as illustrated in FIG. 2B, the surface of the heat exchanger may be reformed to have a hydro-repellent property by allowing the surface of the heat exchanger to have a micro-scale uneven structure.
Third, as illustrated in FIG. 2C, a micronano pattern is formed by performing lithography on the surface of the heat exchanger and then dry-etching the heat exchanger to form a nano structure.
Fourth, as illustrated in FIG. 2D, a nanostructure such as a carbon nanotube (CNT), ZnO, or Si may be vertically grown on a substrate.
However, when a polymer layer with a hydro-repellent property such as a fluorine-substituted polymer is formed as described above, surface characteristics of the polymer layer may be quickly degraded by the repeated cycle of frosting and defrosting. In addition, when a micro nano structure is used, plasma etching or photolithography are required to form the micro nano structure. Thus, the method using the micro nano structure is not suitable for commercial use.